In my experience, driver-based image scaling settings don't work in DX10 and DX11 titles on either Radeons or GeForces. You get full-screen scaling no matter what. Really annoys me when I'm testing at lower resolutions on my 30" panel. I want to see image quality, the effects of different AA modes, and the like, but you can't, really, with scaling active.
I need to ask AMD and Nvidia about it, I guess, but the fact that this behavior has been consistent with DX10 forever and is the same in DX11--and the fact that it affects both major GPU makers--makes me think this is an OS limitation. If any of you all have found a work-around, I'd sure like to know about it. I wouldn't blame just AMD, though.
It might have to do with the removal of the lower level tasks like device enumeration and presenting rendered frames to output from the Direct3D API into the DXGI. See this link
. Maybe in conjunction with the fact that none of the vendors can't seem to get a consistent scaling mode working in Windows 7, developers might have just opted to always set it to be stretched. I imagine that there are less people who complain about the scaling always being stretched than those who will complain that their new shiny game doesn't fill up their monitor. Just stabbing in the dark here.